The present invention relates to a method of manufacturing microglobules by forming a dispersion of droplets of an inorganic phase in an organic phase which is immiscible with water, such that the droplets of the inorganic phase solidify. The solidified droplets are subsequently separated from the organic phase, washed, dried, and optionally subjected to further heat treatment. The watery phase contains inorganic hydrated oxides or components from which they can form and, if required, finely divided carbon. The organic phase is immiscible with water; it has a temperature ranging from 50.degree. to 150.degree. C. and contains, if required, ammonia or an ammonia-releasing agent. With regard to the above, there are several methods in which to dispose the aqueous inorganic phase into or onto the immiscible organic phase and in principle any method of dispersion for manufacturing microglobules is suitable.
Examples of dispersing methods include injection of the inorganic phase into the organic liquid, spraying in the form of droplets over the surface of the organic liquid, and mixing the two phases with the aid of stirrers or the like. Injection may be performed both at the lower end of a column of organic liquid and at the upper end thereof, depending on the respective densities of the two liquids.
Suitable liquids which contain hydrated inorganic oxides include silicon-dioxide sols, hydroxide sols of metals, watery metal-salt solutions, anion-deficient metal-salt solutions, or mixtures of these liquids. The watery phase contains finely divided carbon if carbide particles are to be prepared from the product obtained.
The watery phase or the organic phase optionally contains one or more ammonia-releasing agents, such as urea, hexamethylene tetramine, acetamide, ammonium carbamate, ammonium cyanate or mixtures of such ammonia-releasing agents.
The manufacture of UO.sub.2 microglobules according to one of the prior procedures mentioned above does not produce a consistently uniform and acceptable product. Specifically, defects, principally in the form of cavities, occur in UO.sub.2 globules having an average size of 80-120 microns after sintering. These cavities were presumably caused by the fact that the organic liquid was included therein while the droplets were being formed. According to the method of preparation previously used, one part by volume of a nitrate-deficient uranyl-nitrate solution, UO.sub.2 (OH).sub.0.5 (NO.sub.3).sub.1.5, of 2.85-molar concentration, was mixed, while cooling was being applied, with 1.2 parts by volume of a solution which was 3-molar with respect to both hexamethylene tetramine and urea. The mixed solutions were injected through a cooled stainless steel capillary having a diameter of 0.5 millimeter into an organic liquid at a temperature of 70.degree. C. The globules so produced after separation, washing and sintering exhibited holes and internal cavities after the sintering operation. As a result, the sintered end product had a closed porosity of 6 to 10 percent.
According to U.S. Pat. No. 3,586,742 to Chin et al, oxide microspheres are prepared by injecting droplets of an aqueous metal oxide sol, such as uraniumthorium oxide, into an organic liquid immiscible with the sol, such as kerosene and carbon tetrachloride. The patent states that a surfactant may be added to the organic liquid to prevent coalescing of the droplets and thereby maintain the droplets in the dispersed state. The patent does not exemplify such surfactants, identify suitable surfactants or indicate a suitable quantity needed to prevent coalescing of the droplets.